Field of the Invention
The present invention relates to an antenna structure used in a communication device, such as a folding cellular phone terminal, a method of using the antenna structure and the communication device.
Related Art of the Invention
Downsizing and slimming of cellular phone terminals are being rapidly advanced. In addition, incorporation of an antenna of a cellular phone terminal into a housing thereof is a world trend.
FIG. 19 shows a configuration of an internal antenna of a conventional cellular phone terminal.
FIG. 19(a) is a schematic perspective view of the internal antenna of the conventional cellular phone terminal, and FIG. 19(b) is a side view thereof. In FIGS. 19(a) and 19(b), an antenna element 1201 is to send or receive radio wave from the cellular phone terminal or from another cellular phone terminal, and a shielding case 1206 and a radio circuit for communication 1207 housed in the shielding case 1206 are disposed on a substrate 1202. An LCD 1203 is to display information processed in the cellular phone terminal.
The antenna element 1201 is supplied with power from a feeding point 1204 on the substrate 1202 and has an end electrically connected to a part of the substrate 1202 via a conductive connection 1205. Here, the part of the substrate 1202 and the shielding case 1206 are electrically connected to each other and form a bottom board of the antenna element 1201. Thus, the antenna element 1201, the part of the substrate 1202 and the shielding case 1206 constitutes the internal antenna.
Such a cellular phone terminal has gone beyond serving as a telephone and has been transformed to data terminal equipment that enables transmission of e-mails, browsing of WWW web pages or the like. Thus, upsizing of the display thereof is being promoted.
Under such circumstances, the folding cellular phone terminal has become popular because it is considered to be suitable for downsizing and display upsizing.
Conventionally, the folding cellular phone terminal includes a whip antenna, in addition to the internal antenna. The internal antenna and the whip antenna are used when the cellular phone terminal is folded and when it is not folded, respectively. In general, the impedances of the antennas differ according to whether the cellular phone is folded or not. Thus, the internal antenna and the whip antenna are adjusted to accommodate the difference in impedance, so that the folding cellular phone terminal has a good antenna characteristic both when it is folded and when it is not folded.
FIGS. 20(a)-20(b) show configurations of parts of the folding cellular phone terminal associated with the internal antenna. FIG. 20(a) is a front view of the folding cellular phone terminal and FIG. 20(b) is a side view thereof.
The folding cellular phone terminal has an upper housing 102 and a lower housing 103 coupled with each other by a hinge part 104, and is configured so that the upper housing 102 can be folded on the lower housing 103 via the hinge part 104.
A display 109 is incorporated in the upper housing 102, an upper bottom board 207 is incorporated in the housing at the back side of the display 109, and an upper internal antenna element 205 is incorporated in the housing on a side of the upper bottom board 207 opposite to the display 109.
However, the whip antenna is inconvenient because it needs to be drawn from the housing when the folding cellular phone is used and needs to be retracted into the housing after use. And, the whip antenna has a problem in that such drawing and retraction may cause damage thereto.
Thus, the folding cellular phone terminal has problems in that the whip antenna is burdensome because it needs to be drawn and retracted and that the whip antenna is susceptible to damage due to such operations.
In addition, in the folding cellular phone terminal shown in FIG. 20, the upper internal antenna element 205, the upper bottom board 207 and the lower bottom board 208 constitute the upper internal antenna. In this case, the upper bottom board 207 and the lower bottom board 208 are electrically connected to each other and serve as a bottom board of the upper internal antenna.
When the cellular phone terminal is folded, the antenna bottom board constituted by the upper bottom board 207 and the lower bottom board 208 is also folded. Therefore, the length of the bottom board is about half of that at the time when the cellular phone terminal 201 is not folded. In this case, if the upper bottom board 207 is shorter than a quarter of a wavelength, there is no current standing wave on the bottom board for a desired frequency band, and thus, the bottom board less contributes to radiation of the radio wave from the antenna.
Therefore, in order to use the upper internal antenna both in the states where the cellular phone terminal 201 is folded and is not folded, the antenna needs to have such a wide-band characteristic as to accommodate the difference in the impedance between the cases where it is folded and where it is not folded and the difference in the contribution of the bottom board to the radiation.
That is, since the antenna of the folding cellular phone terminal needs to have a good characteristic both when the cellular phone terminal is folded and when it is not folded, the upper internal antenna becomes large, and in particular, is increased in thickness.
Even if components in the upper housing 102 except for the upper internal antenna, such as display 109, are reduced in thickness, the thick upper internal antenna prevents the upper housing 102 from being slimmed. Similarly, even if components in the lower housing 103 except for the lower internal antenna are reduced in thickness, the thick lower internal antenna prevents the lower housing 103 from being slimmed. Thus, folding portable radio terminals including the folding cellular phone terminal have a problem in that they becomes thick if the internal antenna is used.
In consideration of the problems described above, an object of the present invention is to provide an antenna structure, a method of using the antenna structure and a communication device that eliminate the need to draw and retract an antenna when a folding portable radio terminal is to be used.
Furthermore, in consideration of the problems described above, an object of the present invention is to provide an antenna structure, a method of using the antenna structure and a communication device that enable the folding cellular phone terminal to be further slimmed.
One aspect of the present invention is an antenna structure used in a folding portable ratio terminal, comprising:
a first antenna; and
a second antenna,
wherein said first antenna is used at least when said portable radio terminal is not folded, and
said second antenna is used at least when said portable radio terminal is folded.
Another aspect of the present invention is the antenna structure, wherein when said portable radio terminal is not folded, a diversity reception is carried out with said first antenna serving as a main antenna and said second antenna serving as a sub-antenna, and
when said portable radio terminal is folded, a diversity reception is carried out with said first antenna serving as a sub-antenna and said second antenna serving as a main antenna.
Still another aspect of the present invention is the antenna structure, wherein when said portable radio terminal is not folded, a diversity transmission is carried out with said first antenna serving as a main antenna and said second antenna serving as a sub-antenna, and
when said portable radio terminal is folded, a diversity transmission is carried out with said first antenna serving as a sub-antenna and said second antenna serving as a main antenna.
Yet still another aspect of the present invention is the antenna structure, wherein said first antenna has a better characteristic when said portable radio terminal is not folded, and
said second antenna has a better characteristic when said portable radio terminal is folded.
Still yet another aspect of the present invention is the antenna further structure, further comprising:
a second housing part that incorporates a microphone of said portable radio terminal therein,
wherein said first housing part and said second housing part are capable of being folded,
said first antenna is disposed in said first housing part, and
said second antenna is disposed in said second housing part.
A further aspect of the present invention is the antenna structure, wherein said first antenna is an internal antenna incorporated in said first housing part, and
said second antenna is an internal antenna incorporated in said second housing part.
A still further aspect of the present invention is the antenna structure, wherein said first antenna comprises an antenna element and a bottom board for said antenna element.
A yet further aspect of the present invention is the antenna structure, wherein one of said first and second antennas, which is not used, serves as a passive element for the other, which is used.
A still yet further aspect of the present invention is the antenna structure, wherein when said first housing part and said second housing part are folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, said second antenna is used with said first antenna serving as the passive element, and
when said first housing part and said second housing part are not folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, one of said first and second antennas which has a higher reception level is used with the other, which has a lower reception level, serving as the passive element.
An additional aspect of the present invention is the antenna structure, wherein when said first housing part and said second housing part are folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, one of said first and second antennas which has a higher reception level is used with the other, which has a lower reception level, serving as the passive element, and
when said first housing part and said second housing part are not folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, said first antenna is used with said second antenna serving as the passive element.
A still additional aspect of the present invention is the antenna structure, wherein when said first housing part and said second housing part are folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, said second antenna is used with said first antenna serving as the passive element, and
when said first housing part and said second housing part are not folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, said first antenna is used with said second antenna serving as the passive element.
A yet additional aspect of the present invention is the antenna structure, wherein when said first housing part and said second housing part are folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, one of said first and second antennas which has a higher reception level is used with the other, which has a lower reception level, serving as the passive element, and
when said first housing part and said second housing part are not folded on each other, for reception, diversity reception is carried out at said first antenna and said second antenna, and for transmission, one of said first and second antennas which has a higher reception level is used with the other, which has a lower reception level, serving as the passive element.
A still yet additional aspect of the present invention is an antenna used in a folding portable radio terminal, comprising:
a first housing part that incorporates a speaker therein;
a second housing part that incorporates a microphone therein;
a first antenna; and
a second antenna,
wherein said first housing part and said second housing part are capable of being folded on each other,
said first antenna includes an antenna element and a bottom board for said antenna element,
said antenna element is disposed in said first housing part,
said bottom board is disposed over said first housing part and second housing part,
for a low frequency band, said first antenna is used at least when said first housing part and said second housing part are not folded on each other,
for said low frequency band, said second antenna is used at least when said first housing part and said second housing part are folded on each other,
for a high frequency band, said first antenna is used at least when said first housing part and said second housing part are folded on each other, and
for said high frequency band, said second antenna is used at least when said first housing part and said second housing part are not folded on each other.
A supplementary aspect of the present invention is the antenna structure, wherein for said low frequency band, said first antenna has a better characteristic when said first housing part and said second housing part are not folded on each other, and for said high frequency band, said first antenna has a better characteristic when said first housing part and said second housing part are folded on each other, and
for said low frequency band, said second antenna has a better characteristic when said first housing part and said second housing part are folded on each other, and for said high frequency band, said second antenna has a better characteristic when said first housing part and said second housing part are not folded on each other.
A still supplementary aspect of the present invention is the antenna structure, wherein said antenna which is not used has a load adjusted so that said antenna which is used has a predetermined directivity and a wide band frequency characteristic.
A yet supplementary aspect of the present invention is the antenna structure, wherein a thickness of each of said first antenna and said second antenna is less than a thickness of said portable radio terminal determined by components thereof other than said first and second antennas.
A still yet supplementary aspect of the present invention is the antenna structure, wherein a part of said first housing part and/or second housing part is conductive, and
said conductive part is used as said bottom board.
Another aspect of the present invention is the antenna structure, wherein a part of said first housing part is not conductive, the part facing said antenna element and extending away from a connection of said first housing part with said second housing part from an end of said antenna element opposite to the connection.
Still another aspect of the present invention is the antenna structure, wherein a part of said first housing part which faces said second antenna when said first housing part and said second housing part are folded on each other is not conductive.
Yet still another aspect of the present invention is the antenna structure, wherein whole or a part of said first antenna and/or second antenna is filled with a dielectric.
Still yet another aspect of the present invention is the antenna structure, further comprising:
a display disposed in said first housing part,
wherein said display and said antenna element face each other, and
a part of said display is conductive and serves also as said bottom board.
A further aspect of the present invention is the antenna structure, wherein said display includes a display main body, a frame disposed around said display main body and a reflection plate disposed at the back side of a screen of said display main body, and
whole or a part of said reflection plate is conductive and serves also as said bottom board.
A still further aspect of the present invention is the antenna structure, wherein said display includes a display main body and a frame disposed around said display main body, and
whole or a part of said frame is conductive and serves also as said bottom board.
A yet further aspect of the present invention is the antenna structure, further comprising:
a first housing part that incorporates a speaker of said portable radio terminal; and
a second housing part that incorporates a microphone of said portable radio terminal,
wherein said first housing part serves also as said first antenna, and
said second antenna is a boom antenna disposed in said second housing part.
A still yet further aspect of the present invention is the antenna structure, wherein a part of said first housing part opposite to the side where the display is incorporated is made of a conductive material, and
the part of said first housing part made of a conductive material serves also as said first antenna.
An additional aspect of the present invention is the antenna structure, wherein said first housing part has a slit or slot formed in said part made of a conductive material, and
said first antenna and said second antenna are used for a high frequency band and a low frequency band.
A still additional aspect of the present invention is a method a using an antenna structure used in a folding portable radio terminal, the antenna structure comprising:
a first antenna; and
a second antenna,
wherein said first antenna is used at least when said portable radio terminal is not folded, and
said second antenna is used at least when said portable radio terminal is folded.
A yet additional aspect of the present invention is a method of using an antenna structure, the antenna structure comprising:
a first housing part that incorporates a speaker therein;
a second housing part that incorporates a microphone therein;
a first antenna; and
a second antenna,
said first housing part and said second housing part being capable of being folded on each other,
said first antenna including an antenna element and a bottom board,
said antenna element being disposed in said first housing part, and
said bottom board being disposed over said first housing part and second housing part,
wherein for a low frequency band, said first antenna is used at least when said first housing part and said second housing part are not folded on each other,
for said low frequency band, said second antenna is used at least when said first housing part and said second housing part are folded on each other,
for a high frequency band, said first antenna is used at least when said first housing part and said second housing part are folded on each other, and
for said high frequency band, said second antenna is used at least when said first housing part and said second housing part are not folded on each other.
A still yet additional aspect of the present invention is a communication device, comprising:
the antenna structure according to the 1st invention;
a transmitter circuit that outputs a transmission signal to said first antenna or second antenna; and
a receiver circuit that receives a reception signal received at said first antenna or second antenna.
A supplementary aspect of the present invention is a communication device, comprising:
the antenna structure according to the 13th invention;
a transmitter circuit that outputs a transmission signal to said first antenna or second antenna; and
a receiver circuit that receives a reception signal received at said first antenna or second antenna.